<li>
    <a class="has-arrow" href="javascript:">
        <span class="sidebar-nav-item-icon fa fa-bell fa-lg"></span>
        <span class="sidebar-nav-item">2019</span>
    </a>
    <ul>
        <li>
            <a class="has-arrow" href="javascript:">12</a>
            <ul>
                <li><a class="has-arrow" href="javascript:">1</a>
                    <ul>
                        <li><a class="has-arrow" href="javascript:">0</a></li>
                    </ul>
                </li>
            </ul>
        </li>
    </ul>
</li>


<li>
    <a class="has-arrow" href="javascript:">
        <span class="sidebar-nav-item-icon fa fa-bell fa-lg"></span>
        <span class="sidebar-nav-item">列表3</span>
    </a>
    <ul>
        <li>
            <a class="has-arrow" href="javascript:">项目3-3</a>
            <ul>
                <li><a class="has-arrow" href="javascript:">项目3-3-1</a>
                    <ul>
                        <li><a href="javascript:">项目3-3-1-1</a></li>
                    </ul>
                </li>
            </ul>
        </li>
    </ul>
</li>